[Docs]: Improvements to developer guide

### Doc location

https://github.com/E3SM-Project/simboard/blob/main/docs/developer/README.md

### What is wrong or missing?

1. Automated Metadata Ingestion section needs information about how simboard ingestion state is maintained -- NERSC ingestion job create `/var/lib/simboard-ingestion/state.json` to keep track of ingestion
2. Link to `Make` commands for more useful tips -- maybe do this

### Suggested update

_No response_

### Extra context

_No response_